The present invention relates to a toothed-wheel change gear and, more particularly, to a drive unit formed from an engine, a hydrodynamic torque converter and an automatically shifting toothed-wheel change gear in series with one another in terms of a force flux, with an arrangement for intermediate storage of transmission oil in a gearbox chamber and a gear pump for conveying the transmission oil being arranged in the gearbox chamber.
A toothed-wheel change gear is shown in German Patent Specification 2,939,723 and is arranged with its gear rotation axis, aligned with the axis of rotation of the driving half-shafts of a vehicle axle, parallel to the crankshaft axis and underneath the engine. The force flux from the engine to the gear takes place via a hydrodynamic torque converter flanged with its converter housing to the engine housing. The gearbox is made in one piece with the converter housing. A gearbox wall of the toothed-wheel change gear arranged on the side of the torque converter opposite the engine and located at the same height as the former and a closing cover designed as a pressed sheet-metal part enclose between them a gearbox chamber. In the lower region of the chamber there is at least one storage chamber divided off by retaining walls and intended for the intermediate storage of transmission oil. The middle region of this gearbox chamber receives a valve control housing and a gear pump for supplying pressure to the automatic shift device. The storage chamber is fed with a pressure-relieved oil return flow which comes out of the valve control housing and which is to a greater or lesser extent held back on its way to the lower oil sump by the thermostatic run-off control valve in order to prevent the oil level in the sump from rising as a result of the temperature-related increase in volume.
An object on which the present invention is based, in a drive unit in which an engine, a hydrodynamic torque converter and an automatically shifting toothed-wheel change gear are in series with one another, is essentially to allow a space-saving arrangement of a gearbox chamber for the temperature-dependent intermediate storage of transmission oil above the actual sump, from which the gear pump driven by the engine sucks up transmission oil.
Starting from a toothed-wheel change gear of a generally known type, that object has been achieved in an advantageous way by arranging the gearbox chamber in a constructional space between the converter and the change gear, with a closing cover being adjacent to the converter and the gear pump fastened via its casing to the side of the gearbox wall facing the closing cover. Both the closing cover and the pump casing of the gear pump each have a passage for a pump drive shaft aligned with the gear rotational axis. The pump casing has at least one orifice opening into the gearbox chamber such that the feed to the gearbox chamber is obtained by controlled outflow of leakage oil from the gear pump.
As a result of the present invention, the constructional space present between the converter and gear is used for the immediate storage and the primary pump necessary in any case is used for feeding the relevant gearbox chamber with leakage oil.